The internet is a big network of connected devices, every device has a unique address where others can send information when they want to communicate.
This unique identifier is your IP address and it is automatically assigned to you by your Internet Service Provider (ISP).

Currently most of internet traffic is served over IPv4, consisting in four series of numbers ranging from 0 to 255. There are "only" 4 billion IPv4 adresses, to avoid running out of available addresses IPv6 was developed,
expanding the number to 340 trillion trillion trillion (2128).